Premature Heating Elements Failure.

Seems to me if the elements are rated at 240 vac and you are running them at 415 vac that could be your issue, but I'm not an electrical engineer.

There is a concurrent related thread that gives two methods of wiring groups of (18) elements.

Well... without doing a full analysis and doing up a print to verify... sounds to me like you need to have these elements in a "Wye" configuration and not "delta" of any sort.

Please use a stabilizer. your voltage is surely fluctuating.This is a permanent solution.You have not mentioned the range of Voltage. As a short term measure, you can reduce the supply Voltage of current heaters by 10V. I square value will reduce, so also heating value ,but heaters are not likely to burn.

It hardly matters how much the voltage fluctuates if the OP is supplying the elements at √3x the rated voltage.

The OP hasn't told us the configuration of each element bank, they may well be set up as 240v elements in series pairs, and those then in parallel with similar sets, in which case they should be comfortable with the 415v supply.

I'm just curious as to why they are set up in an open delta arrangement which tends to create an imbalance in circuit currents and a wattage of roughly 3/4 that of a pure delta connected set.

It may simply be that with all elements in operation you are heating them beyond their design capabilities.

It's probably a good time to talk to the element manufacturer for their views on the problem.

Agreed.

Assuming that the OP has given us correct data, then the elements are wrongly connected - Delta connected where they should be Wye......

But assuming they are correctly in a Wye configuration and are not being "over-driven", then it may be a quality issue.

For example, I have had an Italian pellets burner (fantastic to my mind!) since 2007 or thereabouts, and it was supplied new with a Chinese made ignition element (similar to your heating elements but shorter...), which failed after one year (guarantee time here for new is 2 years).

I was sent from the OEM (fom Italy) two new (Chinese again!) elements, identical, but one had a threaded collar/adapter as they were not 100% certain which type my Pellets burner actually needed.

I cut the collar off and then I had two replacements, both of which ran each (one at a time) for about one year before failing (and its only used in winter time!!!).....they also "swelled" at failure, making them difficult to remove and needing a Dremel to cut off the swelling part (sounds painful!) in the grate, before I could remove the rest from the back of the unit. A design failure that after correction means that later pellet burners needed the threaded collar for.....

Which got me through the first three years (winters only!) of usage in total and out of the guarantee!

So then I bought two of the same size and rating, but of German manufacture, and the first one I installed is still running fine!!!! So 4 winters on one element....whether it swells or not at or before failure I cannot (yet) say.....

What country of origin did you use for your elements?

If the answer is Chinese (or any supplier not in Europe or the USA) AND the connection is correctly Wye (I feel it must be or you would to my mind have had a far quicker failure/burnout to my mind), then a lack of quality is probably your problem in my opinion.

Simply buy quality units from a reputable manufacturer and I think your problems will be fixed.....

My experience of element failure is with heat reactivated desiccant compressed air dryers.

Those I worked with were reactivated by purge air passing over a heating element and then hot through the desiccant.

Heaters failed because they got too hot. Either by being undersized (design problem) or run at too high voltage (installation problem) or as often as not, by loss of purge air, or a reduction of purge air flow (on-site tampering).

The latter most likely because a reduction in purge are was economically desirable, but had the knock-on effect of letting the heaters run too hot (a lack of cooling from the heater's point of view) - so they burnt out.

The problem was solved by using heaters that were designed to run at a much higher watt density. The sort that didn't need forced cooling air.

My experience with SiC heating elements required that the elements in each leg had to be resistance matched. Otherwise the imbalance would increase as the elements age causing element overheating and failure.